# FLUX.3 Klein Image Editing API

> FLUX.3 Klein editor with up to 10 references and optional bounding-box object placement

Edits or composes images from a prompt and 1 to 10 references in `image_urls`, which the prompt can cite by order, such as the first image. Up to 32 `bounding_boxes` can keep, move, resize, remove or add objects, named in the prompt by label. Prompt expansion is on by default. It returns 1 to 4 images in jpeg, png or webp.

- Model id: `blackforestlabs/flux-3/klein/edit-image`
- Made by: Black Forest Labs
- Category: Image Editing
- Output: image
- Price per run: from $0.008 / run of output image (cheapest run $0.008 (8 API credits))
- Run: `POST https://api.doitong.com/v1/run/blackforestlabs/flux-3/klein/edit-image`
- Quote: `POST https://api.doitong.com/v1/quote/blackforestlabs/flux-3/klein/edit-image`
- Docs page: https://doitong.com/developers/models/blackforestlabs/flux-3/klein/edit-image

## Pricing

Price: **from $0.008 / run of output image** (the lowest tier; the quote prices your exact input). Price per run: the input files are measured before the run (length, resolution, frame rate). The quote measures the same files and is exactly what the run charges.

The full example input below costs $0.009 = 9 API credits (1 run × $0.009).

Prices are the upstream price in USD, paid from the API balance in API credits (1000 API credits = 1 USD). `POST https://api.doitong.com/v1/quote/blackforestlabs/flux-3/klein/edit-image` with the same JSON body returns the exact price for that input; the quote is exactly what a run charges. Invalid input is never charged and failed or canceled requests are refunded automatically.

## Input parameters

Send either the canonical name or the native field name (not both). Canonical names are the same across models.

| Parameter | Canonical name | Type | Required | Default | Allowed values / range | Description |
|---|---|---|---|---|---|---|
| `prompt` |  | string | yes |  |  | Write a full caption describing the desired image after editing, identifying any references by sequence, such as the first or second image. |
| `enable_prompt_expansion` |  | boolean | no | `true` |  | Prompt expansion into a detailed caption before generation, enabled when true. For editing, the caption is grounded in the reference images. |
| `seed` |  | integer \| null | no |  |  | Seed for reproducible images: an identical prompt and seed produce an identical image when the model version is unchanged. |
| `num_images` | `num_outputs` | integer | no | `1` | 1 – 4 | Image count requested for generation. |
| `enable_safety_checker` |  | boolean | no | `true` |  | Safety checker activation; true enables checking. |
| `output_format` |  | enum (string) | no | `png` | `jpeg`, `png`, `webp` | File format for the resulting image. |
| `image_urls` | `images` | array of image URL | yes |  | 1 – 10 items | Reference images used for editing or composition, limited to 10. |
| `image_size` |  | object {width, height} \| enum (string) \| null | no |  | `square_hd`, `square`, `portrait_4_3`, `portrait_16_9`, `landscape_4_3`, `landscape_16_9` | Output dimensions default to those of the first reference, capped at 1 megapixel for multiple references or scaled to at most 4 megapixels for a sole reference. Explicit sizes must have each side between 256 and 4096 pixels. |
| `bounding_boxes` |  | array of object {label, description, box, source_image_index, source_box, target_box} \| null | no |  | ≤ 32 items | Optional object layout for retaining, moving, resizing, or removing reference objects, or placing new objects. Coordinates start at (0, 0) in each image's top-left corner; refer to boxes using labels in the prompt, such as `<dragon>`. |
| `bounding_boxes[].label` |  | string \| null | no |  | ≤ 64 characters | Brief object label for the box, such as `dragon`; the default is `obj_<n>`. Include `<dragon>` in the prompt to associate its words with the box; boxes not mentioned in the prompt are added to the scene. |
| `bounding_boxes[].description` |  | string | yes |  | ≤ 500 characters | Object to render within the box, including its appearance. |
| `bounding_boxes[].box` |  | object {x_min, y_min, x_max, y_max} \| null | no |  |  | Output placement for the object, replacing `source_box`/`target_box` and using the same placement behavior as text-to-image. |
| `bounding_boxes[].box.x_min` |  | number | yes |  | 0 – 1 | Left boundary expressed relative to image width, from 0 to 1. |
| `bounding_boxes[].box.y_min` |  | number | yes |  | 0 – 1 | Upper boundary expressed relative to image height, from 0 to 1. |
| `bounding_boxes[].box.x_max` |  | number | yes |  | 0 – 1 | Right boundary expressed relative to image width, from 0 to 1. |
| `bounding_boxes[].box.y_max` |  | number | yes |  | 0 – 1 | Lower boundary expressed relative to image height, from 0 to 1. |
| `bounding_boxes[].source_image_index` |  | integer \| null | no |  | ≥ 0 | Object source selection: omit for a new object, or identify an existing reference by its index in `image_urls`, counting from 0. |
| `bounding_boxes[].source_box` |  | object {x_min, y_min, x_max, y_max} \| null | no |  |  | Object location within the reference image; `source_image_index` must also be provided. |
| `bounding_boxes[].source_box.x_min` |  | number | yes |  | 0 – 1 | Left boundary expressed relative to image width, from 0 to 1. |
| `bounding_boxes[].source_box.y_min` |  | number | yes |  | 0 – 1 | Upper boundary expressed relative to image height, from 0 to 1. |
| `bounding_boxes[].source_box.x_max` |  | number | yes |  | 0 – 1 | Right boundary expressed relative to image width, from 0 to 1. |
| `bounding_boxes[].source_box.y_max` |  | number | yes |  | 0 – 1 | Lower boundary expressed relative to image height, from 0 to 1. |
| `bounding_boxes[].target_box` |  | object {x_min, y_min, x_max, y_max} \| null | no |  |  | Output placement box for the object: moving or resizing requires both boxes, while removing a referenced object requires leaving this box unset. |
| `bounding_boxes[].target_box.x_min` |  | number | yes |  | 0 – 1 | Left boundary expressed relative to image width, from 0 to 1. |
| `bounding_boxes[].target_box.y_min` |  | number | yes |  | 0 – 1 | Upper boundary expressed relative to image height, from 0 to 1. |
| `bounding_boxes[].target_box.x_max` |  | number | yes |  | 0 – 1 | Right boundary expressed relative to image width, from 0 to 1. |
| `bounding_boxes[].target_box.y_max` |  | number | yes |  | 0 – 1 | Lower boundary expressed relative to image height, from 0 to 1. |

File parameters (`images`) take a public `https://` URL, a `data:` URI up to 10 MB, or the `file_url` of an upload from `POST /files`.

## Example input

Required parameters only:

```json
{
  "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
  "images": [
    "https://content.doitong.com/images/showcase/v3/gen_fox_cartoon.jpg"
  ]
}
```

A fuller example:

```json
{
  "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
  "image_urls": [
    "https://content.doitong.com/images/showcase/v3/gen_fox_cartoon.jpg"
  ]
}
```

## Run it

Set `DOITONG_API_KEY` to a key from https://doitong.com/developers/dashboard#keys. `?wait=20` returns the finished request in the same call when it is ready within 20 seconds; otherwise poll `GET /requests/{id}` (it also accepts `?wait=`), or pass `webhook_url`.

### curl

```bash
# Run the model; wait up to 20 s for the finished result in the same call
curl -X POST "https://api.doitong.com/v1/run/blackforestlabs/flux-3/klein/edit-image?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
    "image_urls": [
      "https://content.doitong.com/images/showcase/v3/gen_fox_cartoon.jpg"
    ]
  }'

# Still "queued" or "running"? Poll with the id from the response:
curl "https://api.doitong.com/v1/requests/REQUEST_ID?wait=20" \
  -H "Authorization: Bearer $DOITONG_API_KEY"
```

### JavaScript

```javascript
const API = "https://api.doitong.com/v1";
const headers = {
  "Authorization": "Bearer " + process.env.DOITONG_API_KEY,
  "Content-Type": "application/json",
};

// Run the model; wait up to 20 s for the finished result in the same call
let res = await fetch(API + "/run/blackforestlabs/flux-3/klein/edit-image?wait=20", {
  method: "POST",
  headers,
  body: JSON.stringify({
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
    "image_urls": [
      "https://content.doitong.com/images/showcase/v3/gen_fox_cartoon.jpg"
    ]
  }),
});
let request = await res.json();
if (!res.ok) throw new Error(request.error.code + ": " + request.error.message);

// Not finished yet: long-poll until it is
while (request.status === "queued" || request.status === "running") {
  res = await fetch(API + "/requests/" + request.id + "?wait=20", { headers });
  request = await res.json();
}
if (request.status !== "succeeded") throw new Error(JSON.stringify(request.error));
console.log(request.outputs.map((o) => o.url), request.cost.credits + " API credits ($" + request.cost.usd + ")");
```

### Python

```python
import os
import requests

API = "https://api.doitong.com/v1"
headers = {"Authorization": "Bearer " + os.environ["DOITONG_API_KEY"]}

payload = {
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
    "image_urls": [
        "https://content.doitong.com/images/showcase/v3/gen_fox_cartoon.jpg",
    ],
}

# Run the model; wait up to 20 s for the finished result in the same call
r = requests.post(API + "/run/blackforestlabs/flux-3/klein/edit-image", params={"wait": 20}, json=payload, headers=headers)
request = r.json()
if not r.ok:
    raise RuntimeError(request["error"]["code"] + ": " + request["error"]["message"])

# Not finished yet: long-poll until it is
while request["status"] in ("queued", "running"):
    request = requests.get(API + "/requests/" + request["id"], params={"wait": 20}, headers=headers).json()
if request["status"] != "succeeded":
    raise RuntimeError(request["error"])
print([o["url"] for o in request["outputs"]], request["cost"]["credits"], "API credits", "$" + request["cost"]["usd"])
```

### MCP

The MCP server at `https://api.doitong.com/v1/mcp` exposes the tools `search_models`, `get_model`, `quote`, `run`, `get_request`, `cancel_request`, `list_requests`, `create_upload` and `get_account`. A `run` call for this model:

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "run",
    "arguments": {
      "model_id": "blackforestlabs/flux-3/klein/edit-image",
      "input": {
        "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
        "image_urls": [
          "https://content.doitong.com/images/showcase/v3/gen_fox_cartoon.jpg"
        ]
      },
      "wait_seconds": 20
    }
  }
}
```

## Response

Every call returns a request object. `status` is one of `queued`, `running`, `succeeded`, `failed`, `canceled`. `outputs` lists the generated files with URLs on our storage (kept forever, or 7 days with `?storage=temporary`; `storage` says which); `output` is the model's own result object with the same URLs.

```json
{
  "id": "req_8k2m4q7x1z9c3v5b6n0p2r4t",
  "object": "request",
  "model": "blackforestlabs/flux-3/klein/edit-image",
  "status": "succeeded",
  "created_at": "2026-10-20T12:00:00Z",
  "started_at": "2026-10-20T12:00:02Z",
  "completed_at": "2026-10-20T12:00:09Z",
  "queue_position": null,
  "cost": {
    "credits": 9,
    "usd": "0.009",
    "charged": 9,
    "refunded": 0
  },
  "input": {
    "prompt": "A red fox trots through fresh snow at sunrise, soft golden light, shallow depth of field",
    "image_urls": [
      "https://content.doitong.com/images/showcase/v3/gen_fox_cartoon.jpg"
    ]
  },
  "output": {
    "images": [
      {
        "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.jpeg",
        "content_type": "image/jpeg",
        "file_name": "0-output.jpeg",
        "file_size": 1843200,
        "width": 1024,
        "height": 768
      }
    ],
    "timings": {},
    "seed": 42,
    "has_nsfw_concepts": [
      false
    ],
    "prompt": "string"
  },
  "outputs": [
    {
      "type": "image",
      "url": "https://content.doitong.com/dev-api/2026/10/20/req_8k2m4q7x1z9c3v5b6n0p2r4t/0-output.jpeg",
      "content_type": "image/jpeg",
      "file_size": 1843200,
      "width": 1024,
      "height": 768,
      "stored": true
    }
  ],
  "error": null,
  "metrics": {
    "inference_seconds": 6.8
  },
  "urls": {
    "self": "https://api.doitong.com/v1/requests/req_8k2m4q7x1z9c3v5b6n0p2r4t",
    "cancel": "https://api.doitong.com/v1/requests/req_8k2m4q7x1z9c3v5b6n0p2r4t/cancel"
  }
}
```

### Output fields (`output`)

| Field | Type | Description |
|---|---|---|
| `images` | array of object {url, content_type, file_name, file_size, width, height} | Images produced by the model. |
| `timings` | object | Timing information for the generation process. |
| `seed` | integer | Generation seed for the first image. |
| `has_nsfw_concepts` | array of boolean | Indicates whether NSFW concepts appear in the generated images. |
| `prompt` | string | Prompt used during image generation. |

## Related models

- [FLUX.3 Klein](https://doitong.com/developers/models/blackforestlabs/flux-3/klein/text-to-image.md) (`blackforestlabs/flux-3/klein/text-to-image`): from $0.008 / run of output image
- [FLUX.1 Kontext \[pro\]](https://doitong.com/developers/models/flux-pro/kontext.md) (`flux-pro/kontext`): $0.04 / image
- [GPT Image 2.5 Edit](https://doitong.com/developers/models/openai/gpt-image-2.5/flare/edit.md) (`openai/gpt-image-2.5/flare/edit`): from $0.12 / image
- [Nano Banana 2 Edit](https://doitong.com/developers/models/nano-banana-2/edit.md) (`nano-banana-2/edit`): from $0.06 / image
- [Nano Banana Pro Edit](https://doitong.com/developers/models/nano-banana-pro/edit.md) (`nano-banana-pro/edit`): from $0.15 / image
- [Qwen Image 3 Edit](https://doitong.com/developers/models/alibaba/qwen-image-3/edit.md) (`alibaba/qwen-image-3/edit`): from $0.04 / image
- [Seedream 5.0 Pro Edit](https://doitong.com/developers/models/bytedance/seedream/v5/pro/edit.md) (`bytedance/seedream/v5/pro/edit`): from $0.0675 / run of output image
- [FLUX 2 Edit](https://doitong.com/developers/models/flux-2/edit.md) (`flux-2/edit`): $0.012 / megapixel

## Links

- HTML page: https://doitong.com/developers/models/blackforestlabs/flux-3/klein/edit-image
- All models and guides for AI agents: https://doitong.com/developers/llms.txt
- OpenAPI 3.1 with this model's typed request body: https://doitong.com/developers/openapi.json?model=blackforestlabs/flux-3/klein/edit-image
- Errors: https://doitong.com/developers/docs/errors
- Model details as JSON: https://api.doitong.com/v1/models/blackforestlabs/flux-3/klein/edit-image